Some of them are fairly decent. Won't go into the structural aspects as I am sure you can sort that. Don't know the cali building code, but using words like eco friendly, recycling, etc might push you past most problems.
Saw something a few years ago, I think Finland built a big housing complex as a dorm for collage kids. Thought about building Camptainers. Secure hunting and vacation housing.
Concept looks sound. I've only seen beaten up, rusted sea containers. A brand spanking new one may look better. Guess you could replace with a new one in 20 yrs.
Just don't use one for a underground bug-out shelter without reinforcing the thing for the crushing loads of the soil. Heard several horror stories already....
There is an episode of Mythbusters where they are checking the myth about Hitler's assassination attempt at Wolf's lair. They dug out a hole to bury a shipping container in and when Jamie was covering the container it had a structural failure due to the weight of the dirt.
Me personally, I'd like to have a Hobbit hole, no a/c required!
I'd like to make a mobile kitchen with one. Instead of a food truck with taxes and maintenance, just pay a hauler to place the box somewhere for the weekend and make some side dough.
I love the concept. I attempted to get in a Meetup group 10 years ago that had one planned but couldn't get the personnel or funding to get it done.
There is one in Kansas City that was designed and built but by using custom ordered containers from China instead of getting used ones and repurpose them.
I also like the concept of homes made from metal grain bins. Look that one up